dotnet-clean-code

.NET Clean Code Standards

C#-specific coding standards. For universal principles (naming intent, SRP, DRY, error handling), see engineering-principles.mdc.

Conflict resolution: Where this file provides C#-specific guidance that differs from engineering-principles.mdc, this file takes precedence for .cs, .csproj, and .sln files. The universal rule provides the default; this rule provides the override.

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C# naming conventions

• PascalCase: types, methods, properties, constants, public fields
• camelCase: parameters, local variables, private fields (with _ prefix for instance fields)
• I prefix for interfaces: IOrderRepository, not OrderRepository
• Async methods end in Async: GetOrderAsync, SaveChangesAsync
• Boolean properties: IsActive, HasPermission, CanRetry
• Event delegates end in EventHandler; events use past tense: OrderPlaced, PaymentFailed

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Dependency injection

Always inject via constructor; do not use new directly for services.

// Correct
public class OrderService(IOrderRepository repository, ILogger<OrderService> logger) { }

// Incorrect
public class OrderService
{
    private readonly OrderRepository _repository = new OrderRepository();
}

• Use constructor injection; avoid property injection except in framework-controlled types
• Keep constructors lean; inject only what the class needs
• Do not call services inside constructors; defer to method bodies

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Async/await correctness

// Correct: async all the way, CancellationToken passed through
public async Task<Order> GetOrderAsync(Guid id, CancellationToken ct)
    => await _repository.GetByIdAsync(id, ct);

// Incorrect: blocking async call — causes deadlocks
var order = GetOrderAsync(id).Result;

• Always await async calls; never use .Result or .Wait()
• Accept CancellationToken in all public async methods and pass it downstream
• Never use async void except for event handlers; always async Task
• Use ConfigureAwait(false) in library code; not required in ASP.NET Core application code